Soil organic carbon and its influencing factors on the different plant communities in the middle reaches of the Heihe River wetland

Wetlands are one of the important components of the global carbon cycle. They have unique ecological and environmental effects and functions and play an important role in regulating global climate change. In this paper, a wetland in the middle reaches of Heihe River was taken as the research object. Based on field sampling data, plant community sequencing, and structural equation modeling, the soil organic carbon differences and influencing factors of the different plant communities were analyzed. The results showed that there were significant differences in soil organic carbon among the different plant communities in wetland (P < 0.05), and the soil organic carbon content ranged from 3.56～4.30 g·kg ^–1, showing obvious surface aggregation. Soil organic carbon is mainly affected by bulk density, pH, soil total nitrogen, soil moisture, soil available nitrogen, soil salinity, dominant species coverage, total abundance, total coverage, and forb coverage. The contribution of soil physical and chemical properties to soil organic carbon change was 0.55, while the contribution of plant community characteristics to soil organic carbon change was 0.22, indicating that the main reason for soil organic carbon change in plant communities in the middle reaches of Heihe River was the difference in soil physical and chemical properties. The influence of soil physical and chemical properties of soil organic carbon took two different paths: 1) the soil directly affects the physical and chemical properties of soil organic carbon and 2) pH and salt influence the total soil organic carbon abundance. These results show that soil organic carbon change is not the result of a simple direct effect as various influencing factors have indirect effects. The results of this study have certain reference value for soil organic carbon sequestration in wetlands of arid areas.